Comparison of NOx Level and BSFC for HPL EGR and LPL EGR System of Heavy-Duty Diesel Engine

Diesel engines are the most commonly used power plant of freight and public transportations in the world. Also, the newly developed injection system, Common Rail system, increases the demands for both light and heavy duty diesel vehicles. On the other hand, stringent emission regulations are being proposed with growing concern on NO_x and PM emissions from diesel engines. Future emission regulations require advanced emission control technologies, such as EGR and SCR. Exhaust gas recirculation (EGR) is a commonly used technique to reduce NO_x emission. In this paper, a model-based investigation was conducted to compare the effect of high pressure loop (HPL) EGR and low pressure loop (LPL) EGR system on NO_x level and BSFC of a heavy-duty diesel engine. A WAVE model was created to simulate EURO 3 engine and each component of the engine was modeled using CATIA and WaveMesher. A LPL EGR system, which is simulated on a previous study, is compared with a HPL EGR system which uses a variable geometry turbocharger (VGT). Compare to LPL EGR system, HPL EGR system requires higher BSFC penalty to satisfy the same NO_x level. For HPL EGR system, pumping loss seems to be the dominant factor for higher BSFC penalty. For a better understanding, increased intake manifold temperature and pumping loss are discussed to clarify the effect of HPL and LPL EGR system on NO_x level and fuel economy.